Effects of inhaled nanoparticle-rich diesel exhaust on regulation of testicular function in adult male rats

Abstract

We investigated the effects of nanoparticle-rich diesel exhaust (NR-DE) on reproductive function. Eight-week-old male F344 rats were divided into 12 experimental groups and exposed to either whole NR-DE at low (15.37 μg/m³, 2.27 × 10⁵ particles/cm³), middle (36.35 μg/m³, 5.11 × 10⁵ particles/cm³), or high (168.84 μg/m³, 1.36 × 10⁶ particles/cm³) concentrations or clean air for 4, 8, or 12 weeks (5 hours/day, 5 days/week). NR-DE exposure for 4 or 8 weeks did not affect body weight; however, body weight was significantly decreased in rats exposed to low- or high- concentration NR-DE for 12 weeks compared to the control group. Relative weights of testes, epididymides, seminal vesicles, and prostate had increased non-significantly in all NR-DE-exposed rats at 4, 8, and 12 weeks. Adrenal gland relative weights were significantly increased at 4 weeks in rats exposed to low-concentration NR-DE. Plasma luteinizing hormone and follicle stimulating hormone concentrations did not change significantly. Plasma testosterone concentrations were significantly increased after exposure to low- or middle-concentration NR-DE for 4 or 8 weeks compared to controls. Plasma immunoreactive (ir-) inhibin concentrations were significantly increased after exposure to high-concentration NR-DE for 4 weeks or middle- or high-concentration NR-DE for 12 weeks compared to controls. Testicular testosterone concentrations were significantly increased at 4, 8, and 12 weeks after exposure to low-concentration NR-DE compared to controls. In contrast, with exposure to low- or high-concentration NR-DE, testicular ir-inhibin concentrations were significantly greater than in controls, but only at 4 weeks. These results suggest that NR-DE inhalation disrupts the endocrine activity of the male reproductive system.

Acknowledgments

We are grateful to the National Hormone and Pituitary Program, NIDDK, NIH, Torrance, CA, and Dr. A. F. Parlow for the rat LH and FSH RIA kits; and to Dr. G. D. Niswender, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO, USA, for providing antisera to testosterone (GDN 250) and progesterone (GDN 337).

Declaration of interest: This study was supported in part by Grants-in-Aid for Scientific Research (P07582 and B18310044) from the Japan Society for the Promotion of Science (JSPS). The authors alone are responsible for the content and writing of the paper.